1. Field of the Invention
The invention relates to a programmable semiconductor device comprising a supporting member having at least a first line and at least a semiconductor circuit element connected to the line by means of a blowable fuse, in which the blowable fuse is situated at least over a part of its length at a distance from the supporting member or the semiconductor circuit element.
In addition the invention relates to a method of manufacturing such a semiconductor device.
A programmable semiconductor device of the above-mentioned kind may form part, for example, of a programmable read-only memory (PROM). Besides for a programmable read-only memory the programmable semiconductor device may also be used for a logic circuit of the type PLA (programmable logic array) in which the actual logic function of the circuit is established afterwards by means of a programming step.
2. Description of the Prior Art
A programmable semiconductor device of the kind mentioned in the opening paragraph is disclosed in U.S. Pat. No. 3,564,354. In this device the blowable fuse is formed by a narrow thin strip of metal, for example of aluminum, having accurately determined dimensions. Dependent on the information to be written, said fuse is blown selectively by means of current passage. In this device the fuse is covered at its upper side with a passivating layer and is thus partly surrounded by passivating material and in direct contact therewith. As a result of this a part of the energy generated in the metal strip by means of the blowing current is lost as a result of heating of the surrounding passivating layer. Moreover, the fusing time is extended so that writing lasts longer while the device may also be damaged.
If desired, the passivating layer on the upper side of the blowable fuse may be omitted but this is at the expense of the passivation of other parts of the device. Moreover, since the passivating layer is now entirely or partly absent, residues of the blowable fuse may land on the surface of the semiconductor device in the case of blowing and may cause short-circuits or other defects there.